1. Field of the Invention
The present invention relates to an operator's cab (room) in a construction machine such as a hydraulic shovel, a wheel loader or the like.
2. Description of the Related Art
Safety in construction machines has been pursued with increasing vigor in recent years, and various standards have been set forth in order to protect operators or passengers inside the operator's cab by hypothesizing various conditions that may occur during operation at a construction site, such as, for instance, an object falling from above, an object flying from the front, or the machine tipping over. One of such standards, the TOPS (tipping over protective structure) specifies that when the machine body tips over and the tipping load is placed on the upper portion of the side surfaces of the operator's cab of a hydraulic shovel resulting in the frame that constitutes the operator's cab becoming deformed, the deformed member be prevented from entering the vicinity of the operator's seat provided inside the operator's cab from the viewpoint of operator or passenger protection.
The structures adopted for operator's cabs of hydraulic shovels in the prior art include one that is constituted by bonding an inner panel provided toward the operator's cab and an outer panel provided on the outside of the inner panel, and further distending a portion of the inner panel and a portion of the outer panel inward and outward respectively relative to the operator's cab to form hollow pillar portions. In order to satisfy the need for improving the strength of the operator's cab in an operator's cab structure such as this provided with pillar portions, reinforcement member constituted of steel pipe or steel bar may be inserted inside the hollow pillar portions to improve the strength against a tipping load, as disclosed in, for instance, Japanese Laid-open Patent Publication No. Heisei-9-25648.
However, when a commercially available product such as a steel pipe or a steel bar is used as a reinforcement member to be inserted inside a hollow pillar portion, the size of the steel pipe or the steel bar to be used is subject to restriction imposed by the shape of the pillar if the reinforcement member is to be inserted while maintaining the existing pillar shape, and thus, it is difficult to achieve an optimal shape for the pillar portion in terms of strength. In addition, if the pillar shape is changed to accommodate the steel pipe or the steel bar, it will lead to a major design modification and an increase in the production cost.